VSC-HVDC (voltage sourced converter based HVDC) transmission system has technical advantages in the AC and DC system interconnection,large-scale clean energy grid integration.With the application and promotion of the the high-voltage high-capacity multi-terminal VSC-HVDC transmission system,the master station monitoring function is hard to meet their development need.This paper analyzes the topology structure and key equipment features of ±500 kV/3000 MW four-terminal flexible DC power network.In the objective of unmanned converter stations,a monitoring functional framework based on existing monitoring functions of smart grid dispatching and control system (SGDCS) is proposed.Based on the most promising VSC-HVDC grid configuration of half bridge sub-module based modular multilevel converter (HB-MMC)+DC breaker,this paper presents the function schemes for 4 important monitoring modules,grid modeling,data acquisition,topology analysis and intelligent alarming.The proposed monitoring functions would be helpful for the project implementation in the future.